As you probably know, the National Weather Service is a United States Government organization so not many people know. Contact a NWS meteorologist for help.
Meteorologists of the National Weather Service collect data from satellites, instruments attached to weather balloons, and radar. This info. is used to describe weather conditions in the atmosphere...
Satellites. 2nd answer: There is a network of weather reporting stations in the US - many of them at airports - who report temperature, visibility, dew point, wind strength and direction, barometer...
Local National Weather Service stations use Doppler Radar to find local areas of precipitation, hail, severe weather, etc. that they put on weather maps. If it's a nationwide map it probably came...
The National Weather Service makes weather maps with special lines. Isotherm is a line that connects points of equal temperature. Isobar is a line that is drawn to connect equal atmosphere pressure.